32 lines
761 B
TypeScript
32 lines
761 B
TypeScript
/**
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Returns a boolean for whether given two types are equal.
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@link https://github.com/microsoft/TypeScript/issues/27024#issuecomment-421529650
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*/
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type IsEqual<T, U> =
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(<G>() => G extends T ? 1 : 2) extends
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(<G>() => G extends U ? 1 : 2)
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? true
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: false;
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/**
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Returns a boolean for whether the given array includes the given item.
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This can be useful if another type wants to make a decision based on whether the array includes that item.
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@example
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```
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import {Includes} from 'type-fest';
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type hasRed<array extends any[]> = Includes<array, 'red'>;
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```
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@category Utilities
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*/
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export type Includes<Value extends any[], Item> =
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IsEqual<Value[0], Item> extends true
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? true
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: Value extends [Value[0], ...infer rest]
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? Includes<rest, Item>
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: false;
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